1. Field of the Invention
This invention relates to the technique of recovering unutilized energy of water used, for example, in an air-conditioning load in a building, by a hydraulic turbine power generation or the like.
2. Related Art
As an air-conditioning system in a building, there has been extensively used a regenerative heat air-conditioning system in which a heat source machine is operated, utilizing inexpensive midnight power, and the produced heat is stored in a heat storage tank, and in the daytime when an air-conditioning load develops, the stored heat is pumped out, and is fed to an air-conditioner (load), thereby effecting the air-conditioning.
FIG. 16 is a schematic diagram of an open-loop regenerative heat air-conditioning system given as a reference example.
Referring to the construction of a primary system of the regenerative heat air-conditioning system of FIG. 16, reference numeral 16 denotes a water lift pump for pumping water from a heat storage tank 16 and for feeding the water to a heat source machine 4 via a water feed pipe 17, reference numeral 2 an electric motor for driving the water lift pump 1, reference numeral 17 the water feed pipe connecting the water lift pump 1 to the heat source machine 4, reference numeral 3 a commercial power source, reference numeral 5 a two-way valve for adjusting the amount of heat produced by the heat source machine 4, reference numeral 18 a water feed pipe for returning the water, discharged from the heat source machine 4, to the heat storage tank 16, and reference numeral 6 an expansion tank provided on the water feed pipe 18. Reference numeral 29 denotes a float valve, reference numeral 25 a gate valve, and reference numeral 27 a check valve.
Referring to a secondary system of the regenerative heat air-conditioning system of FIG. 16, reference numeral 7 denotes a water lift pump for pumping water (heat) from the heat storage tank 16 and for feeding the water to a group of air-conditioning loads 10 (for example, a plurality of air-conditioning apparatuses such as an air handling unit 10a and a fan coil 10b) via a water feed pipe 19, and reference numeral 8 a double-shaft electric motor which is directly connected at its one end to the water lift pump 7 through a coupling 14 to drive this water lift pump. The other end thereof is connected to a hydraulic turbine 9 via a clutch 13. The hydraulic turbine 9 is located at such a position as to recover the potential energy of water discharged from the group of air-conditioning apparatuses 10. Reference numeral 15 denotes a commercial power source (which may be the commercial source 3). Reference numeral 11 denotes a two-way valve for adjusting the load amount of the group of air-conditioning loads 10, reference numeral 20 a water feed pipe for returning the pumping water, used in the group of air-conditioning apparatuses 10, to the heat storage tank 16, and reference numeral 12 an expansion tank which is provided on the water feed pipe 20, and serves to destroy a siphoning effect so as to exert a head of the fed water (the potential energy of the fed water) on the hydraulic turbine. In some cases, instead of the expansion tank 12, a vacuum breaker is used. Reference numeral 24 denotes a water feed pipe for returning the water, discharged from the hydraulic turbine 9, to the heat storage tank 16. Reference numeral 22 denotes a water feed pipe bypassing the hydraulic turbine 9. Gate valves 21 to 23 are provided on these water feed pipes. Namely, the pumping water, fed to the group of air-conditioning apparatuses 10 by the water lift pump 7, and is used there, and then is fed to the hydraulic turbine 9. The hydraulic turbine 9 is operated by the potential energy of the pumping water to produce power, and transmits this power to the double-shaft electric motor 8. A load of the double-shaft electric motor 8 is made smaller than a load of the water lift pump 7 by this amount. Then, the pumping water, discharged from the hydraulic turbine 9, returns to the heat storage tank 16. Reference numeral 26 denotes a gate valve, reference numeral 28 a check valve, and reference numeral 30 a float valve.
FIG. 17 is a diagram showing operation characteristics of the pump and hydraulic turbine of the reference example. H(m) at an upper portion of an ordinate axis of the diagram represents a total pump head in the case of the pump, and represents an effective head in the case of the hydraulic turbine. P(kw) at a lower portion of the ordinate axis of the diagram represents power for both. An abscissa axis of the diagram represents the water quantity Q. A curve A represents a Q-H performance curve of the pump, and a curve C represents a shaft power curve obtained when the hydraulic turbine is not operated. In the water feed system of FIG. 16, the total pump head H0 is required for feeding the amount Q0 of water by operating only the storage pump 7, and an operating point at this time is a point O4 on the curve A. Power, consumed at this time, is L1 representing the pump shaft power, and an operating point is O1 on the curve C. A curve B represents the effective head (the pressure head difference between the inlet and outlet sides of the hydraulic turbine) of the hydraulic turbine 9, and it means that when the amount Q0 of water is flowed, a pressure difference head (effective head) H1 develops between the inlet and outlet sides of the hydraulic turbine 9, and the hydraulic turbine absorbs this potential energy to produce power L3 described below.
A curve D is a power curve obtained when the storage pump 7 and the hydraulic turbine 9 are operated. Power, produced by the hydraulic turbine 9 when the amount Q0 of water flows, is L3. In this case, the power recovery (L3/L1) is about 20% to about 30%. The operating point at this time is O2 on the curve D, and the consumed power is reduced by L3 relative to L1, and becomes L2 representing the pump shaft power. Energy, corresponding to this power L2, is supplied as electric power from the commercial power source 15.
In the case where a large amount of water flows into the hydraulic turbine, the plurality of apparatuses, described above, are operated in a parallel manner.
There has been proposed another reference example in which a similar system for recovering potential energy of pumping water, passed past a heat source machine, is provided also in a primary system of a regenerative heat air-conditioning system, and this system has been efficiently utilized. Namely, in FIG. 16, the electric motor 2 for driving the water lift pump 1 is modified into the double-shaft type, and the hydraulic turbine 9 is connected to that side of the electric motor 2, which is not connected to the pump, and water, discharged from the heat source machine 4, is received by the hydraulic turbine, and the hydraulic turbine is operated by this pressure head, and a torque, produced by the hydraulic turbine, is transmitted to the electric motor 2, thereby reducing the load (the storage pump 1 in this case) of the electric motor 2. Such conventional examples are disclosed, for example, in JP-A-50-128801 (power recovery pump apparatus) and JP-A-50-49701 (power recovery pump apparatus). A reference example of a hydraulic turbine power-generating system for generating electric power by a hydraulic turbine, provided in a water channel such as a dam and a paddy field, is disclosed in JP-A-5-10245 (outer ring-driving-type hydraulic turbine power-generating apparatus).
In the above reference techniques, however, the clutch is used for connecting the electric motor and the hydraulic turbine together, and a problem to be solved is to improve its transmission efficiency. And besides, there has been encountered another problem that the energy, recovered by the hydraulic turbine, is mechanical power, and therefore can not be used in other loads in a building because of the structure.